A recent communicating system has continuously requested the higher speed and the greater capacity. An optical assembly that includes a semiconductor optical device, such as a laser diode (LD) for emitting light or a photodiode (PD) for receiving light, and a mechanism to couple the semiconductor optical device with an external optical fiber is widely applied in the optical communication system. The optical device often has, what is called, a CAN package, while, the coupling mechanism includes a sleeve to receive the external optical fiber, a skirt to receive the CAN package and a lens integrally formed with the sleeve and the skirt.
A Japanese Patent Application published as JP-2010-107692A has disclosed an optical assembly having the optical device and the coupling mechanism. FIG. 15 schematically illustrates, in a cross section thereof, the optical assembly disclosed in the prior art above. The optical assembly 100 includes a holder 110 and an optical device 102 that installs a semiconductor optical device 103 therein. The holder 110 includes a sleeve 112, a lens 113, and a skirt 114. Another Japanese Patent Application published as JP-2007-155973A has disclosed a method to produce an optical assembly, where the semiconductor optical device practically emits light in a process to align the holder with the optical device. Sliding the semiconductor optical device in a plane perpendicular to the optical axis of the device and monitoring the light provided from a tip end of the optical fiber, the optical device is assembled with the holder at a center of the symmetrical distribution of the field pattern of the light.
In order to obtain a desired coupling efficiency between the optical device and the external optical fiber for the optical assembly disclosed in the former prior art, the semiconductor device 103 is preferably positioned on the focal point of the lens 113. Specifically, the semiconductor device 103 is necessary to be positioned around the focal point of the lens 113 within about 10 μm in a case where the external optical fiber is, what is called, a multi-mode fiber. However, the installation of the optical device 103 within the optical device 102 inherently shows alignment tolerance comparable to or greater than the limitation above.
The method to produce the optical assembly disclosed in the latter prior art is not only necessary to activate the semiconductor device practically and to prepare an apparatus to monitor the amplitude of the light, but the method takes a long time to determine the optimal position. Embodiments of the present invention are to provide an improved arrangement of the holder and a method to produce the optical assembly.